1990-1995 Corvette ZR-1 - Regal Beginnings

A Look Back At The Original King Of The Hill: The '90-'95 ZR-1

The first "Phase I" LT5 engines were installed by Lotus in standard-bodied '86 coupes like the one shown here.

The letter "Z" attached to a Corvette has always denoted enhanced performance and exclusivity, and the '09 ZR-1 is no exception. As was the case with the ZR-1 model that hit the market nearly 20 years ago, this 638hp super-Vette commands huge sums over sticker for the privilege of ownership. But the original King of the Hill shares more with its successor than an ability to stoke the passions of collectors. Its advanced performance technology continues to influence current Corvettes and the hardware that motivates them. The real story of the '90-'95 ZR-1 is how this technology was developed.

It all began when Dave McLellan became Corvette's chief engineer in 1975. McLellan inherited a chassis that was introduced in 1963 and a body that was restyled in 1968. He knew the clock was ticking on the C3 design, so he immediately began work on the C4. McLellan and his team started with a clean sheet of paper. The car's aerodynamic drag was reduced, thanks to a raked windshield and a smaller front end. The chassis made extensive use of aluminum and other weight-saving materials. Electronics helped cut emissions and fuel consumption. When the car was introduced to the public in the spring of 1983, it received rave reviews for its handling but garnered considerable criticism for its lack of power. McLellan knew the car needed an engine producing well over 300 hp, and he pushed Director of Powertrain Engineering Russ Gee to come up with a solution.

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(From left) Gordon Killebrew, Gib Hufstader, and Dave McLellan were all integral parts of the ZR-1 development team. Killebrew wrote the technical manuals for the car, Hufstader was the LT5 packaging engineer, and McLellan was the chief engineer.

Gee developed a few turbocharged V-6 and V-8 prototype engines for testing, but concerns over cost and reliability ultimately ruled out the forced-induction approach. Gee then turned to engineer Tony Rudd from Lotus Engineering, a company GM owned at the time. In November 1984, during a visit to Detroit, Rudd described the DOHC 4.0L V-8 the British manufacturer was devel-oping. It produced 350 hp-close to what McLellan wanted to slip into the C4 chassis. Gee initially thought Lotus could build cylinder heads to add to the Corvette's existing 350 small-block, but it was soon discovered that this was not the case. The only option was to craft a completely new block to accept the Lotus DOHC heads. Approval to build the engine was granted, and the process began in August 1985. The goal was to have the first engine running by May the following year.

The first "Phase I" LT5 engine ran for 30 minutes on May 1, 1986. Track testing began at Lotus in the summer, when the company received a shipment of engineless component cars from GM. Twenty-five of these standard-bodied ZR-1 test cars were built and subsequently used by Lotus and GM for development purposes. As far as we know, only one remains: a yellow car currently in the hands of a British collector.

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The early test engines were hand-built in England by Lotus techs, under the supervision of GM powertrain engineers.

Meanwhile, testing continued on the Phase I and, later, Phase II LT5 engines. During this time, considerable effort was devoted to packag-ing the accessories and solving the engine's persistent oiling problems. Since the LT5 would be built in limited numbers and installed strictly in the Corvette, GM selected an outside contrac-tor to construct it. In March 1986, Mercury Marine in Stillwater, Oklahoma, was approved as the sole builder of the LT5 powerplant.

ZR-1 chassis development was also well underway at the time. Since GM was already using the SCCA's showroom-stock racing series to validate the endurance of the standard C4, it was a relatively simple matter to secretly install LT5 engines in some of these cars for testing between races. Additionally, two showroom-stock Morrison Corvettes were fit-ted with modified, 500hp small-blocks and raced at Daytona and Sebring. These races provided GM engineers with valuable data on the car's chassis strength and durability.

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1990-1995 Corvette ZR-1 - Regal Beginnings

The first "Phase I" LT5 engines were installed by Lotus in standard-bodied '86 coupes like the one shown here.

(From left) Gordon Killebrew, Gib Hufstader, and Dave McLellan were all integral parts of the ZR-1 development team. Killebrew wrote the technical manuals for the car, Hufstader was the LT5 packaging engineer, and McLellan was the chief engineer.

The early test engines were hand-built in England by Lotus techs, under the supervision of GM powertrain engineers.

When the testing program was completed, GM ordered Lotus to destroy all of its prototypes. Believe it or not, this car would eventually be restored-in fact, it's the same one shown in this article's lead photo.

In 1986, two Morrison Motorsports showroom-stock Corvettes were converted to ZR-1 chassis testbeds. Each was fitted with a 500hp engine and raced at Daytona and Sebring. This car finished Third in the GTO class and Seventh overall at the Sebring race.

Collector Tyler Townsley owns this '88 prototype ZR-1 (No. EX5014). The car was built in Bowling Green in the summer of 1987 and used for electrical testing. It's the only original nonrestored preproduction ZR-1 in private hands.

The interior of the Snake Skinner was Spartan, to say the least. The car had no A/C, radio, or center console. These and other changes reduced weight from 3,600 to 2,700 pounds.

Assistant Corvette Engineer John Heinricy modified this ZR-1 prototype into the legendary "Snake Skinner." He used this car to evaluate how a Corvette could be made to outperform the Dodge Viper.

This production-ready ZR-1 was featured at the '89 Geneva Auto Show. It now resides at the National Corvette Museum.

This bare ZR-1 chassis was also unveiled at the '89 Geneva show. The display has since been fitted with wheels and a center console from a '93 model.

Twenty-Five ZR-1s were shipped to Carcasonne, France, later that year, to allow a select group of journalists to preview the new model. This one-chassis No. 3-was among that group.

In March 1990, this prototype '87 ZR-1 was fitted with a production LT5 engine and used to break three 50-year-old speed records. The car averaged 175.885 mph for 24 hours on a Fort Stockton, Texas, test track.

This car, chassis No. 3, is the lowest-production-number '89 ZR-1 in existence. It's currently a part of GM's Heritage Collection.

When the ZR-1's '89 production run was canceled, the existing cars were scrapped or used for testing. One ended up in the hands of race engineer Ryan Falconer, who stuffed it with this 680hp V-12 engine. The car's front chassis had to be stretched 8 inches to accommodate the longer engine.

In August 1989, a small number of '90 "Active Suspension ZR-1" prototypes were built at the Bowling Green plant. If produced, this suspension system would have been a $39,000 option. Note the front scoops and extra fender vents for cooling.

Here's what the Active Suspension cars looked like under the hood. How would you like to change the spark plugs on this beast?

This GM display shows the complexity of system's left rear corner.

Four '90 ZR-1 convertibles were built to evaluate whether the topless chassis was strong enough to handle the LT5 engine. It wasn't, and the car was never produced. This prototype has been fitted with '95 wheels and is currently in the GM Heritage Collection.